1. Field of the Invention
This invention relates to a feeder/transporter for feeding sheets seriatim from a stack and transporting the sheets along a path, and more particularly to a valve-controlled rotary vacuum sheet feeder/transporter.
2. Description of the Prior Art
In many applications in the printing and copy/duplicating fields, it is necessary to feed sheets seriatim from a stack and thence transport the sheets along a path to a remote location. Apparatus for feeding and transporting sheets are generally either of a mechanical or of a vacuum type. Mechanical equipment, such as scuff feeders or belt transports, require frictional interaction with the sheet to induce movement of the sheet. Vacuum apparatus on the other hand use pneumatic forces to maintain a sheet in contact with a feeder or transporter as the feeder or transporter is moved.
As may be readily appreciated, feeding sheets from a stack presents different handling problems than transporting sheets along a travel path. In feeding sheets from a stack, it is generally necessary to insure that only one sheet is fed at a time, with the position of a sheet being of secondary consideration; on the other hand, in transporting sheets, it is often necessary to provide accurate control over the position of the sheet without consideration for multiple sheet handling. The mechanical and vacuum apparatus each have certain advantages to recommend their use for feeding or transporting sheets, and either type may be selected for a particular application depending upon the overall design considerations of the equipment in which it is to be used.
It is desireable to use vacuum apparatus as feeders in situations where feeding of such sheets seriatim is of particular importance. Such apparatus can be controlled to accurately pick single sheets from a stack. While mechanical feeders could also be employed, a double sheet rejection mechanism is usually required to assure single sheet feeding. Vacuum apparatus also have advantages in transporting sheets in a curved path in that positive control of a sheet may be maintained from one side of the sheet (as opposed to contacting the sheet on both sides thereof). However, as noted above, in utilizing vacuum apparatus, movement of the apparatus must be provided in order to cause the sheets to move. Furthermore, in transferring sheets from one portion of the apparatus to another, such as between one transporter and a subsequent transporter functioning at a higher transport speed, it is desireable that the vacuum for the first transporter be cut off after the second transporter receives the sheet to prevent drag on the sheet.